Controllable Acceleration and Deceleration of Charge Carrier Transport in Metal‐Halide Perovskite Single‐Crystal by Cs‐Cation Induced Bandgap Engineering

Abstract

Charge carrier transport in materials is of essential importance for photovoltaic and photonic applications. Here, the authors demonstrate a controllable acceleration or deceleration of charge carrier transport in specially structured metal‐alloy perovskite (MACs)PbI3 (MA= CH3NH3) single‐crystals with a gradient composition of CsPbI3/(MA1−xCsx)PbI3/MAPbI3. Depending on the Cs‐cation distribution in the structure and therefore the energy band alignment, two different effects are demonstrated: i) significant acceleration of electron transport across the depth driven by the gradient band alignment and suppression of electron–hole recombination, benefiting for photovoltaic and detector applications; and ii) decelerated electron transport and thus improved radiative carrier recombination and emission efficiency, highly beneficial for light and display applications. At the same time, the top Cs‐layer results in hole localization in the top layer and surface passivation. This controllable acceleration and deceleration of electron transport is critical for various applications in which efficient electron–hole separation and suppressed nonradiative electron–hole recombination is demanded.

Metal Halide Perovskite Alloy: Fundamental, Optoelectronic Properties and Applications

“…[150] In a smoothly gradient bandgap, a significantly accelerated electron transport is achieved rate, up to 1.5 Â 10 10 s À1 of transport rate. [151] The increased carrier mobility will be greatly beneficial for photovoltaic and detector applications. Interestingly, in a thin thickness of the gradient layer of (MA 1Àx Cs x )PbI 3 (Figure 6d), a deceleration of electron Figure 6.…”

“…transport and thus enhanced electron-hole recombiantion is observed due to energy barrier formed at the interfce, which is benefitical for electron-hole recombination and therefore largely increases the emission efficiency and will be beneficial for LED and laser applications. [151] The alloy MHPs with gradient bandgap exhibits unique carrier dynamics and excellent performance. As mentioned above, the performances of MHPs based devices closely depend on the carrier dynamics, which suggest that the accelerated carrier transport can be used to fabricate high performance devices.…”

“…[ 150 ] In a smoothly gradient bandgap, a significantly accelerated electron transport is achieved rate, up to 1.5 × 10 10 s −1 of transport rate. [ 151 ] The increased carrier mobility will be greatly beneficial for photovoltaic and detector applications. Interestingly, in a thin thickness of the gradient layer of (MA 1− x Cs x )PbI 3 (Figure 6d), a deceleration of electron transport and thus enhanced electron‐hole recombiantion is observed due to energy barrier formed at the interfce, which is benefitical for electron‐hole recombination and therefore largely increases the emission efficiency and will be beneficial for LED and laser applications.…”

“…Interestingly, in a thin thickness of the gradient layer of (MA 1− x Cs x )PbI 3 (Figure 6d), a deceleration of electron transport and thus enhanced electron‐hole recombiantion is observed due to energy barrier formed at the interfce, which is benefitical for electron‐hole recombination and therefore largely increases the emission efficiency and will be beneficial for LED and laser applications. [ 151 ]…”

Challenges in the development of metal-halide perovskite single crystal solar cells

“…97 In general, in the applications of photovoltaics and detector, efficient separation of the photgenerated charge carriers and their quick transport to the respective charge carrier collecting layers is highly desirable. 98…”