報告書番号

T97075

タイトル（和文）

色素増感型湿式太陽電池の効率向上方策の理論的検討

タイトル（英文）

THEORETICAL STUDY OF MEASURES TO INCREASE THE ENERGY-CONVERSION EFFICIENCY OF DYE-SENSITIZED NANOCRYSTALLINE PHOTOELECTROCHEMICAL CELLS

概要 （図表や脚注は「報告書全文」に掲載しております）

多孔質酸化チタン膜での電荷移動と光散乱の理論的な解析から，色素増感太陽電池の効率向上方策を提案した。多孔質半導体電極での電荷移動の解析をするために，蓄電池の多孔質電極の理論を応用し新しい理論モデルを導出した。この理論モデルを用いて文献での実験データから同電池を解析した。半導体電極内での電流損失は，従来の常識とは大きく異なり，無視できるほど小さくない。この電流損失は，従来の湿式太陽電池の理論と異なる，印加電圧に依存しないプロセスである。上記の電流損失の低減と光エネルギーの吸収率の増加を実現できる新しいタイプの電池構造を，酸化チタン微粒子の光散乱効果の理論的な解析を基に考案した。この構造は，酸化チタン薄膜による光の後方散乱と硝子基板／酸化チタン界面の全反射による光閉じ込め効果により，従来より薄膜の多孔質膜で長波長領域の光の吸収を増やすことができる。

概要 （英文）

EFFECTIVE MEASURES TO INCREASE THE ENERGY-CONVERSION EFFICIENCY OF DYE-SENSITIZED NANOCRYSTALLINE PHOTOELECTROCHEMICAL CELLS ARE PROPOSED BASED ON A THEORETICAL ANALYSIS OF CHARGE TRANSPORTATION AND SCATTERING OF LIGHT IN TI02 FILMS. TO ANALYZE CHARGE TRANSPORTATION IN DYE-SENSITIZED NANOCRYSTALLINE TI02 ELECTRODES, A NEW THEORETICAL MODEL BASED ON BATTERY THEORIES IS DEVELOPED. THE RECOMBINATIONPROCESS AT THE SEMICONDUCTOR-ELECTROLYTE INTERFACE IN DYE-SENSITIZED NANOCRYSTALLINE PHOTOELECTROCHEMICAL CELLS IS EXAMINED WITH THE MODEL. THE DIFFUSION LENGTH IN THE DYE-SENSITIZED POROUS TI02 FILMS UNDER THE SHORT-CIRCUIT CONDITION, ESTIMATED FROM THE ACTION SPECTRA, IS SMALLER THAN THE FILM THICKNESS EVEN IN THE CELLS WITH THE HIGHEST EFFICIENCY. WHEN THE RECOMBINATION IS INDEPENDENT OF THE APPLIED POTENTIAL, THE HIGHOPEN-CIRCUIT VOLTAGE CAN BE ATTAINED EVEN IF THE RECOMBINATION CURRENTUNDER ILLUMINATION IS MUCH LARGER THAN THE REVERSE SATURATION CURRENT IN DARKNESS. TO DECREASE THE RECOMBINATION CURRENT UNDER A SHORT-CIRCUIT CONDITION, USE OF THINNER TI02 NANOCRYSTALLINE FILMS IS EFFECTIVE. A NEW STRUCTURE OF A DYE-SENSITIZED NANOCRYSTALLINE PHOTOELECTROCHEMICAL CELL, WHICH PERMITS EFFECTIVE ABSORPTION OF INCIDENT SOLAR ENERGY USINGTHINNER DYE-SENSITIZED FILM, IS PROPOSED BASED ON THEORETICAL EXAMINATION. THE CELL EFFECTIVELY CONFINES INCIDENT LIGHT IN THE THINNER DYE-SENSITIZED FILM BY MULTIPLE SCATTERING FROM DISPERSED TI02 PARTICLES AT THE BOTTOM, AND TOTAL REFLECTION BETWEEN THE INSERTED TI02 FILM AND THE GLASS SUBSTRATE AT THE SURFACE. UNDER POTIMAL SCATTERING CONDITIONS, THE BACKSCATTERED INTENSITY IS MAXIMIZED WHEN THE BACKSCATTERING ANGLE ISEQUAL TO THE CRITICAL ANGLE OF REFLECTION AT THE SURFACE. THE OPTICAL CONFINEMENT IS ALSO EFFECTIVE FOR LONG-WAVELENGTH LIGHT.

報告者

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