Long, balanced electron and hole diffusion lengths greater than 100 nanometers in the polycrystalline organolead trihalide compound CH3NH3PbI3 are critical for highly efficient perovskite solar cells. We found that the diffusion lengths in CH3NH3PbI3 single crystals grown by a solution-growth method can exceed 175 micrometers under 1 sun (100 mW cm(-2)) illumination and exceed 3 millimeters under weak light for both electrons and holes. The internal quantum efficiencies approach 100% in 3-millimeter-thick single-crystal perovskite solar cells under weak light. These long diffusion lengths result from greater carrier mobility, longer lifetime, and much smaller trap densities in the single crystals than in polycrystalline thin films. The long carrier diffusion lengths enabled the use of CH3NH3PbI3 in radiation sensing and energy harvesting through the gammavoltaic effect, with an efficiency of 3.9% measured with an intense cesium-137 source.
Organic-inorganic halide perovskites (OIHPs) bring an unprecedented opportunity for radiation detection with their defect-tolerance nature, large mobility-lifetime product, and simple crystal growth from solution. Here we report a dopant compensation in alloyed OIHP single crystals to overcome limitations of device noise and charge collection, enabling γ-ray spectrum collection at room temperature. CHNHPbBr and CHNHPbCl are found to be p-type and n-type doped, respectively, whereas dopant-compensated CHNHPbBrCl alloy has over tenfold improved bulk resistivity of 3.6 × 10 Ω cm. Alloying also increases the hole mobility to 560 cm V s, yielding a high mobility-lifetime product of 1.8 × 10 cm V. The use of a guard ring electrode in the detector reduces the crystal surface leakage current and device dark current. A distinguishable Cs energy spectrum with comparable or better resolution than standard scintillator detectors is collected under a small electric field of 1.8 V mm at room temperature.
high-throughput fabrication of perovskite modules has also been demon strated with simple processes such as blade coating with module efficiency close to 15%. [8] It remains unclear as to whether the perovskite solar cells can operate over 25 years in a real-world environment that is filled with oxygen and moisture, which are their two major stressors. Enhanced encapsulation has clearly shown to elongate the operational lifetime of perovskite solar cells to a much longer duration, indicating that the intrinsic stability of perovskite solar cells may be much longer than expected. [9][10][11] Nevertheless, perovskite solar cells may find their niche applications in space where oxygen or moisture does not exist. For space applications, there are new stressors such as radiation that may impose new threats to the stability of perovskite solar cells, while stability of solar cells under radiation has been rarely studied. The increasing interest in perovskite-based X-ray and gamma-ray detectors warrants an imperative study of the stability of perovskite materials and devices under ionizing radiation. [12,13] Less than a handful of studies have been performed to reveal the effects of proton, electron, and X-ray irradiation on perovskite so far. [14][15][16][17] Miyazawa et al. irradiated perovskite solar cells with 1 MeV electrons and found that the devices retained 93% of their peak performance after irradiation with a fluence of 1 × 10 16 cm −2 . [15] Experiments conducted by Lang et. al. [14] indicated a decrease in short-circuit current density (J SC ) by 20% for perovskite solar cells exposed to a proton dose of 1 × 10 13 p cm −2 . The perovskite self-healed with recovery on fill factor (FF) and open-circuit voltage (V OC ) after the proton irradiation terminated. [16] The effects of soft X-ray exposure on uncovered perovskites were investigated by Motoki et al. who reported that soft X-ray irradiation resulted in the evaporation of perovskite surface with residual elements in the form of crystalline PbI 2 . Apart from above stability studies with different radiation sources, the stability of perovskite device under gamma-ray radiation is also important but remained virtually unexplored. [18] Large amounts of gamma-rays are inevitably produced when the galactic cosmic rays, comprising mainly protons and alpha particles, undergo nuclear interactions with the constituent nuclei of the spacecraft, which poses a challenge to the perovskite materials for their long-term application in space. Moreover, organohalide perovskites also showed great Organohalide metal perovskites have emerged as promising semiconductor materials for use as space solar cells and radiation detectors. However, there is a lack of study of their stability under operational conditions. Here a stability study of perovskite solar cells under gamma-rays and visible light simultaneously is reported. The perovskite active layers are shown to retain 96.8% of their initial power conversion efficiency under continuous irradiation of gamma-rays and light for...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.