Development of the non-destructive and 3-dimentional profile investigation of the non-radiative recombination in the nano-structure inserted solar cells

2020 Fiscal Year Final Research Report

• Project/Area Number: 16H04648
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Energy engineering
• Research Institution: University of Miyazaki
• Principal Investigator: Fukuyama Atsuhiko 宮崎大学, 工学部, 教授 (10264368)
• Project Period (FY): 2016-04-01 – 2021-03-31
• Keywords: 非発光再結合過程 / 超高効率量子ナノ太陽電池 / 非破壊且つ非接触評価技術 / レーザーヘテロダイン検出

Outline of Final Research Achievements

The role of a GaAs strain-relaxation interlayer inserted into InGaAs/GaAsP superlattice solar cells was evaluated by measuring the piezo-electric photothermal (PPT) signals. The PPT signals caused by the non-radiative recombination of electrons photo-excited to the first quantized level were observed. The temperature-dependent PPT signal intensities were assessed using an electron carrier relaxation model. Although the non-radiative recombination remained dominant around room temperature, tunneling of carriers through the e2-miniband after thermal excitation from the e1-level increased and became comparable. This implies that the recombination loss of the photo-excited carriers is suppressed by the insertion of the GaAs interlayer.
Laser heterodyne photothermal displacement method was developed and adopted to n-type Si. Obtained surface displacements well corresponded to the theoretical calculation results based on the thermal diffusion equation.

Free Research Field

半導体物性工学

Academic Significance and Societal Importance of the Research Achievements

量子ナノ太陽電池で十分な変換効率が得られていない理由は光吸収層に挿入する量子井戸や量子ドット、超格子構造の物性評価が不十分なためである。これら量子ナノ構造はLEDやLDなど発光デバイスに既に実装されているが、注入キャリアの発光再結合のみに注目したものである。一方、太陽電池では量子ナノ構造内に発生した光励起キャリアの再結合を抑制しつつ数十層もの量子ナノ構造中を輸送させるという非常に複雑なデバイス動作が必要であり、得られた成果は学術的にも非常に興味深い。また、非発光再結合に伴う表面変位量を非接触且つサブナノオーダーで高感度検出できる手法の確立は、様々な学術分野に応用できるポテンシャルを持つ。