CsPbI2Br quantum dots integration for high performance organic photovoltaics and photodetectors†

Abstract

Organic semiconductors promise highly-flexible, solution-processible electronics, and have attracted great attention in applications for photovoltaics and photodetectors. However, they also suffer from large exciton binding energy and poor charge transport ability, meaning they cannot compare with traditional inorganic alternatives. In this work, CsPbI₂Br inorganic perovskite quantum dots (PQDs) were integrated into cutting-edge polymer:non-fullerene photoactive films to improve the performance of both photovoltaic (PV) and photodetecting (PD) devices. We find there is strong energy transfer from these PQDs to the donor component PM6, which results in an improved short-circuit current and photoresponsivity in PV and PD devices, whilst strong chemical interactions between PQDs and fullerene acceptor L8-BO are revealed, passivating the defects of PQDs. Mott–Schottky measurements, in conjunction with electrochemical impedance spectroscopy, further elucidate that a wider depletion region is established with the assistance of PQDs, attributed to the above interaction and larger dielectric constant enabled by PQDs, which could be the key to the accelerated charge transport and reduced charge recombination. With the integration of PQDs, an improvement in power conversion efficiency from 18.8% to 19.4% (maximum 20.2% for D18:L8-BO) is observed in PM6:L8-BO PV devices, whilst a decrease in dark current from 1.5 × 10⁻⁵ to 9.6 × 10⁻⁷ mA cm⁻² at −0.1 V is obtanied in PD devices, translating to a superior detectivity of 6.5 × 10¹² Jones at 770 nm.