Organic solar cells and perovskite solar cells lose power in strikingly different ways when trap-assisted recombination takes hold, according to a modeling study published in Applied Physics B. Using a basic drift–diffusion framework, Jovana Gojanović, Milan Stanojević and Petar Matavulj show that Shockley-Read-Hall (SRH) recombination through trap states mainly erodes the short-circuit current of organic solar cells, while in perovskite devices it predominantly suppresses the open-circuit voltage. In both cases the losses translate into a significant reduction of efficiency, but the underlying physics turns out to be almost a mirror image between the two technologies.
The team built their analysis on a standard drift–diffusion model, combining the Poisson equation with continuity equations for electrons and holes and drift–diffusion expressions for the two current densities. Generation of charge carriers was calculated with the Beer–Lambert law, transport layers and interfacial processes were deliberately left out, and SRH recombination was assumed to act through a single discrete trap level in the active layer. Organic devices were simulated with recombination via deep traps, consistent with literature reports of deep traps 0.36 to 0.7 electronvolts below the transport edge, while perovskites were treated as dominated by shallow traps, which recent studies indicate govern recombination dynamics in those films. The equations were solved with a finite difference scheme, the Scharfetter–Gummel approach and a Newton algorithm.
Trap density was swept from 10^13 to 3×10^18 per cubic centimeter, a range the authors say corresponds to values reported in the literature for both material classes. In the organic solar cell, raising the trap density visibly dragged down both the short-circuit current and the fill factor, while the open-circuit voltage declined only modestly. The perovskite cell behaved in the opposite manner: its short-circuit current barely moved as SRH recombination increased, but the open-circuit voltage loss was substantial, and the fill factor fell far less than in the organic device. These simulated current–voltage curves form the core evidence for the paper’s central claim about where each technology bleeds performance.
Because charge carrier mobility is one of the fundamental differences between organic materials and perovskites, the researchers made it the axis of a second investigation. Mobility values were varied from 10^-4 to 10 square centimeters per volt-second, and the losses of short-circuit current and open-circuit voltage caused by moving trap density from 10^13 to 3×10^18 per cubic centimeter were tracked as functions of mobility. Across this range, the perovskite device suffered larger absolute losses than the organic one. At a mobility of 10^-3 square centimeters per volt-second, the perovskite lost roughly 10 milliamperes per square centimeter of short-circuit current and about 0.17 volts of open-circuit voltage, compared with roughly 3.66 milliamperes per square centimeter and about 0.08 volts for the organic cell. The perovskite losses also fell more steeply as mobility increased.
The explanation lies in what happens inside each device at short circuit. When the cell is unbiased, the difference in work functions between anode and cathode creates a built-in voltage and an internal electric field that separates electrons and holes and tends to deplete the active region. In the organic cell, low mobility means many carriers linger in the active layer, and SRH recombination at trap states thins their numbers. That depletion linearizes the electrostatic potential and homogenizes the electric field, although the field integral over the layer, equal to the built-in voltage, stays the same. Crucially, removing carriers lowers the conductivity of the active layer, which reduces the drift component of the current both inside the device and in the external circuit. The diffusion component, by contrast, is independent of SRH recombination, so the short-circuit current falls as the drift current shrinks.
The perovskite cell tells a different short-circuit story. Its much higher carrier mobility sweeps charges out of the active region quickly, leaving few carriers available to recombine at trap states or directly with one another. Changing the SRH recombination rate therefore leaves the electrostatic potential profile, the electric field profile, the conductivity and the drift current essentially untouched, and since the diffusion current is likewise constant, the short-circuit current does not change. The simulated SRH recombination rate in the organic device, around 10^21 per cubic centimeter per second, was an order of magnitude higher than in the perovskite, around 10^20, and it peaked in the central part of the organic active layer, whereas in the perovskite it concentrated near the electrode contacts where carriers accumulate.
At open circuit, defined as zero net current at the open-circuit voltage, the drift current must balance the diffusion current in both device types. Because that diffusion current does not depend on SRH recombination, the required balance is fixed, so a recombination-driven drop in conductivity forces the electric field to strengthen. Since the open-circuit voltage equals the built-in voltage minus the field integral across the active layer, a stronger field means a lower open-circuit voltage. The diffusion current is much larger in the perovskite, owing to its higher mobility and longer diffusion length, so the electric field there is larger and the voltage drop across the active region is bigger. A given conductivity change therefore shifts the field more strongly in the perovskite, which is why its open-circuit voltage loss is the more pronounced one.
Mobility itself turned out to be a double-edged parameter for perovskites. Increasing it improves carrier separation and depletes the active layer, producing field and potential profiles that resemble those caused by raising trap density. But carriers that leave the active layer thanks to higher mobility contribute to the external current, while carriers lost to recombination are simply gone, a distinction captured by the layer’s conductivity, which rises with mobility and falls with trap density. The simulations also revealed a curious effect: higher mobility in perovskites enhances carrier diffusion, and at open circuit the drift component must grow to match it, strengthening the electric field and lowering the open-circuit voltage, a phenomenon other authors have described as well. Yet when trap density was raised to 3×10^18 per cubic centimeters, devices with higher mobility still performed better than low-mobility ones.
To check that these predictions are not artifacts of a stripped-down model, the authors compared them with experimental data from the literature. The simulated current–voltage curves reproduced measured curves for a specific organic cell and a specific perovskite cell. They also compiled relative improvements in open-circuit voltage and short-circuit current from five high-efficiency organic solar cell studies in which trap density was reduced through ternary blends, additives or optimized acceptors, and from perovskite studies using passivation strategies such as additive engineering, chelating coordination, bifunctional molecular modulation, diammonium bonding and pyridine-based co-passivation. In the organic devices, suppressing SRH recombination boosted the short-circuit current more than the voltage; in the perovskites, the voltage gained more than the current. Both patterns matched the model’s predictions.
The authors are careful about the limits of their framework. The model omits the structural and energetic disorder that fundamentally shapes organic devices, excludes ion migration in perovskites even though it influences performance even without prominent hysteresis, ignores transport layers and interfacial processes, and represents traps as a single discrete level rather than a continuous distribution. They argue these simplifications limit quantitative precision but should not alter the core qualitative trends, since adding disorder would mainly soften the current–voltage curves and lower fill factors, while ionic migration and interfacial recombination would shift performance metrics further. Because real devices involve additional effects beyond the calculations, the conclusions remain qualitative rather than strictly quantitative. Even so, the study offers a clear physical baseline: the same trap-driven loss mechanism bends organic and perovskite solar cells in opposite directions, and the disparity in carrier mobility between the two material classes is what bends them.
Subject of Research: Modeling how Shockley-Read-Hall recombination affects the current-voltage behavior of organic and perovskite solar cells
Article Title: The impact of SRH recombination on the current–voltage characteristic of organic and perovskite solar cells: a basic drift–diffusion framework
Article References: Gojanović, J., Stanojević, M., & Matavulj, P. (2026). The impact of SRH recombination on the current–voltage characteristic of organic and perovskite solar cells: a basic drift–diffusion framework. Applied Physics B, 132(11), Article 117. https://doi.org/10.1007/s00340-026-08722-0
Image Credits: AI Generated
DOI: 10.1007/s00340-026-08722-0
Keywords: organic solar cells, perovskite solar cells, Shockley-Read-Hall recombination, drift-diffusion model, trap density, charge carrier mobility, open-circuit voltage, short-circuit current, photovoltaics, device physics, trap states, power conversion efficiency
News Source: Denise Maddox. (November 6, 2026). Trap Recombination Hits Organic and Perovskite Solar Cells in Opposite Ways. Scienmag.
