Quantum-assisted photoelectric gain effects in perovskite solar cells

Further boosting the power conversion efficiencies (PCEs) of perovskite solar cells (PSCs) without excessively increasing production expenses is critical for practical applications. Here, we introduce silicon quantum dots (SiQDs) to enable perovskites to harvest additional sunlight without changing PSC processes. These SiQDs can convert shorter wavelength excitation light (300–530 nm) into visible region light and reflect longer wavelength perovskite-unabsorbed visible light (550–800 nm), leading to broadband light absorption enhancement in PSCs. As a result, the SiQD-based photocurrent gain can improve the external quantum efficiencies of PSCs over a wide wavelength range of 360–760 nm, yielding relatively enhanced short-circuit current density (+1.66 mA/cm2) and PCE (+1.4%). Surprisingly, even the PSC with a low-purity perovskite layer shows an ultrahigh PCE improvement of 5.6%. Our findings demonstrate QD-assisted effects based on earth-abundant and environmentally friendly silicon, leading to effective optical management that remarkably promotes the performance of PSCs and enables the balance of costs to be substantially addressed. A sunlight management strategy in perovskite solar cells (PSCs) using silicon quantum dots (SiQDs) is proposed. Due to the reabsorption of visible light induced by SiQDs, the external quantum efficiency spectra of PSCs in a wide wavelength range of 360–760 nm is significantly improved, resulting in facilitated photocurrent collection and enhanced performance of SiQD-based PSCs. Combining new and traditional solar cell materials improves the efficiency of energy conversion. Perovskites, materials with the same type of crystal structure as calcium titanium oxide, have become recognized as excellent materials for photovoltaics in particular. The ideal solar cell must optimize the amount of electrical power generated as a fraction of the solar energy striking its surface. However, most semiconductors only absorb a small proportion of the light, and this limits efficiency. A Japan-Taiwan cooperation team led by Kazuhito Tsukagoshi (National Institute for Materials Science), Chun-Wei Chen (National Taiwan University) and colleagues added silicon nanoparticles to perovskite solar cells to absorb a broader spectrum of light and thus improve its performance. In total, silicon nanoparticles can convert the shorter wavelength light to perovskite abosorbable range, and also reflect the visible light into perovskites.