Indoor organic and perovskite photovoltaics (PVs) have been attracting great interest in recent years. The theoretical limit of indoor PVs has been calculated based on the detailed balance method developed by Shockley–Queisser. However, realistic losses of the organic and perovskite PVs under indoor illumination are to be understood for further efficiency improvement. In this work, the efficiency limit of indoor PVs is calculated to 55.33% under indoor illumination (2700 K, 1000 lux) when the bandgap (E_g) of the semiconductor is 1.77 eV. The efficiency limit was obtained on the basis of assuming 100% photovoltaic external quantum efficiency (EQE_PV) when E ≥ E_g, there was no nonradiative recombination, and there were no resistance losses. In reality, the maximum EQE_PV reported in the literature is 0.80–0.90. The proportion of radiative recombination in realistic devices is only 10^-5–10^-2, which causes the open-circuit voltage loss (ΔV_loss) of 0.12–0.3 V. The fill factor (FF) of the indoor PVs is sensitive to the shunt resistance (R_sh). The realistic losses of EQE_PV, nonradiative recombination, and resistance cause the large efficiency gap between the realistic values (excellent perovskite indoor PV, 32.4%; superior organic indoor PV, 30.2%) and the theoretical limit of 55.33%. In reality, it is feasible to reach the efficiency of 47.4% at 1.77 eV for organic and perovskite photovoltaics under indoor light (1000 lux, 2700 K) with V_OC = 1.299 V, J_SC = 125.33 µA/cm², and FF = 0.903 when EQE_PV = 0.9, EQE_EL = 10^-1, R_s = 0.5 Ω cm², and R_sh = 10⁴ kΩ cm².

In recent years, significant progress has been achieved in the design and fabrication of stretchable optoelectronic devices. In general, stretchability has been achieved through geometrical modifications of device components, such as with serpentine interconnects or buckled substrates. However, the local stiffness of individual pixels and the limited pixel density of the array have impeded further advancements in stretchable optoelectronics. Therefore, intrinsically stretchable optoelectronics have been proposed as an alternative approach. Herein, we review the recent advances in soft electronic materials for application in intrinsically stretchable optoelectronic devices. First, we introduce various intrinsically stretchable electronic materials, comprised of electronic fillers, elastomers, and surfactants, and exemplify different intrinsically stretchable conducting and semiconducting composites. We also describe the processing methods used to fabricate the electrodes, interconnections, charge transport layers, and optically active layers used in intrinsically stretchable optoelectronic devices. Subsequently, we review representative examples of intrinsically stretchable optoelectronic devices, including light-emitting capacitors, light-emitting diodes, photodetectors, and photovoltaics. Finally, we briefly discuss intrinsically stretchable integrated optoelectronic systems.In recent years, significant progress has been achieved in the design and fabrication of stretchable optoelectronic devices. In general, stretchability has been achieved through geometrical modifications of device components, such as with serpentine interconnects or buckled substrates. However, the local stiffness of individual pixels and the limited pixel density of the array have impeded further advancements in stretchable optoelectronics. Therefore, intrinsically stretchable optoelectronics have been proposed as an alternative approach. Herein, we review the recent advances in soft electronic materials for application in intrinsically stretchable optoelectronic devices. First, we introduce various intrinsically stretchable electronic materials, comprised of electronic fillers, elastomers, and surfactants, and exemplify different intrinsically stretchable conducting and semiconducting composites. We also describe the processing methods used to fabricate the electrodes, interconnections, charge transport layers, and optically active layers used in intrinsically stretchable optoelectronic devices. Subsequently, we review representative examples of intrinsically stretchable optoelectronic devices, including light-emitting capacitors, light-emitting diodes, photodetectors, and photovoltaics. Finally, we briefly discuss intrinsically stretchable integrated optoelectronic systems.

Solution processible photovoltaics (PV) are poised to play an important role in scalable manufacturing of low-cost solar cells. Electrospray is uniquely suited for fabricating PVs due to its several desirable characteristics of an ideal manufacturing process such as compatibility with roll-to-roll production processes, tunability and uniformity of droplet size, capability of operating at atmospheric pressure, and negligible material waste and nano structures. This review begins with an introduction of the fundamentals and unique properties of electrospray. We put emphasis on the evaporation time and residence time that jointly affect the deposition outcome. Then we review the efforts of electrospray printing polymer solar cells, perovskite solar cells, and dye sensitized solar cells. Collectively, these results demonstrate the advantages of electrospray for solution processed PV. Electrospray has also exhibited the capability of producing uniform films as well as nanostructured and even multiscale films. So far, the electrospray has been found to improve active layer morphology, and create devices with efficiencies comparable with that of spin-coating. Finally, we discuss challenges and research opportunities that enable electrospray to become a mainstream technique for industrial scale production.