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Hole transport layer (HTL) plays a critical role for achieving high performance solution-processed optoelectronics including organic electronics. For organic solar cells (OSCs), the inverted structure has been widely adopted to achieve prolonged stability. However, there are limited studies of p-type effective HTL on top of the organic active layer (hereafter named as top HTL) for inverted OSCs. Currently, p-type top HTLs are mainly 2D materials, which have an intrinsic vertical conduction limitation and are too thin to function as practical HTL for large area optoelectronic applications. In the present study, a novel self-assembled quasi-3D nanocomposite is demonstrated as a p-type top HTL. Remarkably, the novel HTL achieves ≈15 times enhanced conductivity and ≈16 times extended thickness compared to the 2D counterpart. By applying this novel HTL in inverted OSCs covering fullerene and non-fullerene systems, device performance is significantly improved. The champion power conversion efficiency reaches 12.13%, which is the highest reported performance of solution processed HTL based inverted OSCs. Furthermore, the stability of OSCs is dramatically enhanced compared with conventional devices. The work contributes to not only evolving the highly stable and large scale OSCs for practical applications but also diversifying the strategies to improve device performance.

The change in doping density in P3HT:PCBM based polymer solar cells (PSCs) with different processing solvents and with/without post-fabrication thermal treatment is investigated with capacitance-voltage measurement and optical microscopic imaging. The results suggest that both slow drying and thermal treatment facilitate the phase-separation and crystallinity of P3HT and PCBM, leading to low defect density and thus low p-type doping. Direct links between the doping density and the performance of the PSCs, specifically the short-circuit current (Jsc) and open-circuit voltage (Voc), are observed. The results show that doping density is one of the decisive factors affecting the photocurrent of the PSCs. Lower doping density leads to a wider depletion region, which is beneficial for carrier collection. The agreement between the calculation and the experiment suggests that the Voc increases monotonically with increasing doping densities in the PSCs. These rules consistently explain our results on the change of Jsc and Voc after thermal annealing in the PSCs with different processing solvents.

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The graphene oxides are abundant in hydroxyl and carboxyl groups that are close to the reactive dyes. These structural features gave a possibility to modify textiles to enhance the conductivity by using the dyeing and finishing method. Herein, graphene modified cotton textiles are fabricated by soaking cotton cloth in graphene oxide colloid. After reduction, the modified textiles exhibit an improved conductivity. The present work contributed a facile strategy for graphene modified textiles.