Charge Generation and Recombination in High Fullerene Content Organic Bulk Heterojunction Solar Cells

Abstract

Organic bulk heterojunction solar cells with a high fullerene content (larger than 70%) have been studied in this work. The device performances of this kind of solar cell could be tuned by adjusting the blend ratio in the active layer. An appropriate amount of p-type semiconductor in the high fullerene content active blend layer is beneficial for light absorbance and exciton dissociation. The proper energy alignment between the highest occupied molecular orbital of a p-type material and an n-type fullerene derivative has a strong influence on the exciton dissociation efficiency. In addition, the mechanism of photogenerated charge recombination in the solar cells has been identified through intensity-dependent current density–voltage ( J–V ) measurements and results show that the mechanisms governing the recombination are crucial for solar cell performance.

Highly Efficient (>9%) Lead‐Free AgBiS2 Colloidal Nanocrystal/Organic Hybrid Solar Cells

“…As shown in Figure 3d, the FF of control devices (i.e., without 2‐ME treatment) was impaired at higher light intensities, implying that an unfavorable energy alignment caused non‐geminate charge recombination under forwarding bias. [ 19 ] In contrast, the FF of 2‐ME‐treated devices was almost unchanged with respect to the light intensity, implying that non‐geminate recombination was suppressed as the energy‐level mismatch was relieved. Moreover, as shown in Figure 3e, the ideality factor obtained from J SC as a function of the light intensity significantly increased from 0.755 to 0.972 with 2‐ME treatment, indicating that the bimolecular recombination of the device was reduced.…”

Stable P3HT: amorphous non-fullerene solar cells with a high open-circuit voltage of 1 V and efficiency of 4%

“…In case of trap-assisted recombination, FF deteriorates with reducing incident light intensity as the proportion of free charges recombining with trapped charges increases. 49,50 As shown in Fig. 3c, the device 1 (P3HT:SF-HR as-cast device) and device 2 (P3HT:SF-HR annealed device) showed different patterns.…”