Enhanced Open-Circuit Voltage in Colloidal Quantum Dot Photovoltaics via Reactivity-Controlled Solution-Phase Ligand Exchange.

Jo, Jea Woong; Kim, Younghoon; Choi, Jongmin; de Arquer, F Pelayo García; Walters, Grant; Sun, Bin; Ouellette, Olivier; Kim, Junghwan et al. · Adv Mater · 2017

basic_science · Level V

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Abstract

The energy disorder that arises from colloidal quantum dot (CQD) polydispersity limits the open-circuit voltage (V<sub>OC</sub> ) and efficiency of CQD photovoltaics. This energy broadening is significantly deteriorated today during CQD ligand exchange and film assembly. Here, a new solution-phase ligand exchange that, via judicious incorporation of reactivity-engineered additives, provides improved monodispersity in final CQD films is reported. It has been found that increasing the concentration of the less reactive species prevents CQD fusion and etching. As a result, CQD solar cells with a V<sub>OC</sub> of 0.7 V (vs 0.61 V for the control) for CQD films with exciton peak at 1.28 eV and a power conversion efficiency of 10.9% (vs 10.1% for the control) is achieved.