Sogabe TOHMA (曽我部 東馬)

Self-consistent drift–diffusion model has been widely employed to simulate the device performance of intermediate band solar cell (IBSC) under practical device configuration. However, one of the remained issues in the drift–diffusion modeled-based works is the difficulty to reach the IB carrier continuity through the self-consistent manner. In most of the previous reports the constraints were relaxed or just partially satisfied; which render the unreliable performance results and misguide the device design strategy. In this work, in order to solve this issue and to validate our results, we performed extensive simulations to fully disclose the significant effect of the IB continuity constraints by taking InAs/GaAs quantum dot-based IBSC as a model device using the semiconductor modules in COMSOL Multiphysics combined with the Fortran codes. We found that under rigorous satisfaction of IB continuity constraint, the band potential profiles for the IBSC with either doped or nondoped IB under various light illumination conditions are nearly identical to those under the dark conditions. Moreover, from the simulated current–voltage curve dependence on the light concentration ratio, we found the device performance based on drift–diffusion under rigorous IB continuity constraint showed similar tendency to the features simulated based on detailed balance principle except the much-lowered power conversion efficiency. Our work demonstrated here, serves as an accurate and reliable IBSC device design approach toward better IB material screening, efficiency improvement, optical management, and extended application in the emerging field such as the perovskite material-based IBSC.

Recent experimental results suggest that higher mobility of perovskite-type ligand passivated PbS quantum dots (QDs) could be useful for efficient solar cell applications. However, theoretical understanding of the mechanism through first principal modeling is still lacking. In this study, electronic-, optical-, and temperature-dependent carrier mobility for perovskite ligand passivated PbS QD array is calculated by using the first-principles density functional theory (DFT) combined with the nonequilibrium Green’s function (NEGF) technique and a molecular dynamics (MD)-Landauer approach. It is found that formamidinium (FA)-liganded QDs have higher mobility and enhanced optical absorption comparing to that of Cl-liganded QDs. The difference could be understood through the intermediate band featured electronic structure.

A deep understanding of the effect of the A-site cation cross-exchange on the hot-carrier relaxation dynamics in perovskite quantum dots (PQDs) has profound implications on the further development of disruptive photovoltaic technologies. In this study, we investigated the hot carrier cooling kinetics of pure FAPbI3 , MAPbI3 , CsPbI3 and alloyed FA0.5 MA0.5 PbI3 , FA0.5 Cs0.5 PbI3 , and MA0.5 Cs0.5 PbI3 QDs using ultrafast transient absorption (TA) spectroscopy. The lifetimes of the initial fast cooling stage (<1 ps) of all the organic cation-containing PQDs were shorter than those of the CsPbI3 QDs, as verified by the electron-phonon coupling strength extracted from the temperature-dependent photoluminescence spectra. The lifetimes of the slow cooling stage of the alloyed PQDs were longer under illumination greater than 1 sun, which was ascribed to the introduction of co-vibrational optical phonon modes in the alloyed PQDs. This facilitated efficient acoustic phonon upconversion and enhanced the hot-phonon bottleneck effect, as demonstrated by first-principles calculations. This article is protected by copyright. All rights reserved.

Offer Organization: 日本学術振興会, System Name: 科学研究費助成事業, Category: 基盤研究(B), Fund Type: -, Overall Grant Amount: - (direct: 14200000, indirect: 4260000)
本研究では，再生可能エネルギーを主力電源化するために必須となる，小規模に自立分散化した多数の創・蓄電群（グリッド）を自在にネットワーク接続してインフラ化する革新的エネルギープラットフォームを実現するための，安定供給とレジリエンスを実現する最適制御方法を確立する．特に，都市部の壁面への設置を前提として，時間，季節，設置壁面の方角によって発電量の異なる太陽電池群と，小規模な蓄電池群によるシステムを用いて，不確実なエネルギー環境を安定かつレジリエントに利用する制御プロトコルおよびアルゴリズムを開発，実装し，その有効性を明らかにする．
初年度となるR5年度は，本提案の実証環境の設計と，統合分配機能，制御方法などの基本機能を設計を実施した．アモルファス・シリコン，およびペロブスカイト太陽電池を使った円筒形太陽電池の壁面設置方式の検討と，試作による検証を実施した．また，関連する環境データと発電量のモニタリングに対するシステム設計を行い，一部の実験を完了した．
また，都市レベルの壁面発電の発電量を評価する3D都市モデルシミュレーションや，円筒形太陽電池の設置方式による受光量への影響を検討する受光量シミュレーションを作成し，小規模自立分散化した創・蓄電群のエネルギー創出効果の評価を開始した．実際に壁面に設置する円筒形太陽電池については，アモルファス・シリコン太陽電池に加えて，ペロブスカイト太陽電池セルを採用するための検討をじ実施し，試作の上で実証に用いる目処をつけた．
統合分配機能については，MQTTを用いたネットワークを介して，設定コストとリンク効率を考慮した電力供給経路の選択手法を検討し，その効果を評価した．現在，実機による検証の準備を進めている．