Engineering the Non‐Radiative Recombination of Mixed‐Halide Perovskites with Optimal Bandgap for Indoor Photovoltaics

Abstract

Indoor photovoltaics have attracted increasing attention, since they can provide sustainable energy through the recycling of photon energy from household dim lighting. However, solar cells exhibiting high performance under sunlight may not perform well under indoor light conditions, mainly due to the mismatch of the irradiance spectrum. In particular, most of the indoor light sources emit visible photons with negligible near‐infrared irradiance. According to the detailed balance theory, the optimal bandgap for indoor photovoltaics should be relatively larger, considering the trade‐off between photocurrent and photovoltage losses. In this work, a systematic comparison of the theoretical limits of the conventional and indoor photovoltaics is presented. Then the non‐radiative recombination losses are reduced by a synergetic treatment with Pb(SCN)2 and PEABr, resulting relatively high open circuit voltage of 1.29 V and power conversion efficiency of 17.32% under 1 sun illumination. Furthermore, the devices are fully characterized under weak indoor light (1000 lux, 4000 K LED) achieving a high efficiency of 37.18%, which is promising for real applications.

Perspectives for the conversion of perovskite indoor photovoltaics into IoT reality

“…8,59 Based on the calculated optimal E g value of perovskites under indoor light illumination, Li et al tailored the perovskite com-position to modify the bandgap of perovskite. 60 The incorporation of Cs and Br could increase the E g value to be around 1.77 eV, i.e., FA 0.8 Cs 0.2 Pb(I 0.6 Br 0.4 ) 3 , which enhanced the device performance under weak indoor light. Furthermore, the complete substitution of organic cations (MA + or FA + ) by inorganic cation Cs + can easily widen the perovskite bandgap, which can tune the bandgap range from 1.73 eV (CsPbI 3 ) to 2.3 eV (CsPbBr 3 ).…”

Recent Strategies for High-Performing Indoor Perovskite Photovoltaics

“…The photovoltaic performance of a device with a certain bandgap is significantly dependent on the type of lamps used and is very sensitive to illumination intensity. Based on the calculated PCE as a function of the band gap derived from the Shockley–Queisser limit, a maximum theoretical PCE of approximately 33% under AM 1.5G is achieved for materials with a 1.20–1.40 eV bandgap [ 32 ], whereas PCEs of 45.70%, 47.70%, and 58.40% under FL, phosphorous LED, and red-green-blue LED, respectively, are achieved for materials with an optimal bandgap of 1.70–2.00 eV [ 33 ]. Figure 1 b shows the PCE as a function of the bandgap for AM 1.5G and white LED.…”

“…( b ) Energy gap vs. calculated power conversion efficiency (PCE) derived from S–Q limit of an ideal solar cell under AM 1.5G and 4000 K white light emitting diode (LED; grey area depicted different of those ideal bandgaps). Reprinted with permission from [ 32 ], copyright 2022 John Wiley and Sons.…”

“…Lead thiocyanate (Pb(SCN) 2 ) additives were used in PPVs [ 85 , 86 , 87 ] to increase the grain size, improve crystallinity, and produce excess PbI 2 , which is beneficial for grain boundary passivation. The same method was employed for Id-PPVs by adding Pb(SCN) 2 as a bulk additive and PEABr for surface modification [ 32 ]. Similarly, Pb(SCN) 2 additives increased the grain size and crystallinity, and the PEABr surface treatment further improved the photoelectrical properties by passivating defects at the perovskite surface.…”

“…Furthermore, among all indoor photovoltaics, indoor perovskite photovoltaics (Id-PPVs) exhibit the highest PCEs of over 40% under indoor light [ 30 , 31 ], which are suitable for wireless and self-powered IoT sensors. However, there are still rooms for further improvements in Id-PPVs to achieve better stability and higher efficiency derived from the Shockley-Queisser limit under indoor light illumination [ 32 , 33 ].…”