Quantum dot-sensitized solar cells: A review on interfacial engineering strategies for boosting efficiency

Quantum dot-sensitized solar cells (QDSSCs) have become important in dealing with the energy-economy-environment dilemma of today’s world. QDSSCs offer a unique set of characteristics including multiple exciton generation and higher extinction coefficients associated with quantum dots (QDs), avowing its potential for high photoconversion efficiency (PCE), which is evident from its augmented increase of the PCE to ∼ 15 % within the past decade. To make full use of the photoelectrochemical competence of QDSSCs, researchers have strategically dealt with various detrimental events taking place within QDs and on interfacial positions in photoanodes. Back transfer of photogenerated electrons, electron/hole recombination via surface defects, and photocorrosion of QDs seriously deteriorate the performance of QDSSCs and are thus considered a bottleneck for their further improvements. Deposition of interfacial layers (ILs) has proven beneficial in this regard and hence, it requires a comprehensive overview. Based on their positions inside the photoanode of QDSSCs, ILs offer single or multiple roles in improving the PCE: improvement of surface passivation (passivation ILs), deposition of QDs (seeding ILs), and/or control of the back transfer of electrons to the electrolyte (blocking ILs). This review covers the multifunctional diversity of ILs inside QDSSCs, apposite characterization techniques for ILs, and prospects regarding their role.