Origin of Open‐Circuit Voltage Turnover in Organic Solar Cells at Low Temperature

Abstract

While the efficiency of organic solar cells (OSCs) has increased considerably in recent years, there remains a significant gap between the experimental open‐circuit voltage (VOC) and the theoretical limit. Understanding the origin of this energy loss is important for the future development of OSCs, with temperature‐dependent measurement of VOC an important approach to help unlock the underlying physics. Interestingly, previous studies have observed a reduction in VOC at low temperature that has been attributed by different studies to different phenomena. To resolve this issue, herein the temperature dependence of VOC of various polymer‐based OSC systems covering a range of acceptor types (fullerene, polymer, and non‐fullerene small molecule) as well as device architectures (conventional, inverted, blend and bilayer) is studied. Across all systems studied, VOC reduction at low temperatures is associated with high parasitic leakage current, providing a universal explanation for this phenomenon in OSCs. Moreover, it is shown that leakage current, which causes complexity in the analysis and raises reliability concerns in potential applications, can be suppressed by varying device architecture, providing an effective approach for analyzing the true temperature dependence of VOC.

Printable and Semitransparent Nonfullerene Organic Solar Modules over 30 cm2 Introducing an Energy-Level Controllable Hole Transport Layer

“…Also, pristine HTL Solar was introduced as above, and the slope (α) values were 0.968, 0.795, and 0.983, respectively. In general, when the slope values of kT / q are closer to 1.0, suppressed trap-assisted recombination is observed, and when the slope value of α is closer to 1.0, suppressed bimolecular recombination is exhibited. − The h-HTL-incorporating devices showed excellent dependent property with suppressed carrier recombination properties. Furthermore, the measurement of dark J – V curves of the fabricated devices showed a low leakage current under reverse bias and high current density under forward bias for the h-HTL-incorporating devices (Figure S15).…”

“…With the measurement of the dependence of V OC and J SC under various illumination conditions, the carrier recombination properties of the pristine HTL Solar and h-HTL-incorporating devices were analyzed (Figures e,f and S14). For light intensity ( I ), the relationship of V OC ∝ kT / q ln­( I ) is satisfied. , As optimum h-HTLs were introduced in the SMD2, P­(Cl–Cl)­(BDD = 0.2), and PM6-based photoactive layers, the slope values were 1.090 kT / q , 1.084 kT / q , and 1.042 kT / q , respectively. Also, pristine HTL Solar was introduced as above, the slope values were 1.154 kT / q , 1.134 kT / q , and 1.107 kT / q , respectively.…”

“…For light intensity (I), the relationship of V OC ∝ kT/q ln(I) is satisfied. 62,63 As optimum h-HTLs were introduced in the SMD2, P(Cl−Cl)(BDD = 0.2), and PM6-based photoactive layers, the slope values were 1.090kT/q, 1.084kT/q, and 1.042kT/q, respectively. Also, pristine HTL Solar was introduced as above, the slope values were 1.154kT/q, 1.134kT/q, and 1.107kT/q, respectively.…”

Different Morphology Dependence for Efficient Indoor Organic Photovoltaics: The Role of the Leakage Current and Recombination Losses

“…We have confirmed E CT trend for our blend films by employing temperature-dependent V OC measurements. 42,58 Temperature-dependent J−V curves are illustrated in Figure S6. V OC shows a linearly increasing trend for each device from room temperature right down to 80 K, displayed in Figure 3c.…”

The Graphene Structure’s Effects on the Current-Voltage and Photovoltaic Characteristics of Directly Synthesized Graphene/n-Si(100) Diodes

“…That is because U OC , differently from the I SC , usually is decreased due to the tunneling [ 110 ]. Reduced U OC with increased leakage current was reported for multi-crystalline silicon [ 111 ], organic [ 112 , 113 ], and graphene/GaAs [ 114 ] solar cells.…”