[en] We have developed an improved method for easily determining the photoluminescence quantum efficiencies of transparent materials, such as solutions, glass plates, and thin films on a substrate, having various absorbances from ca. 0.05 to 1.0 at the excitation wavelength when reabsorption is negligible. The estimated accuracy for emitting semiconductor nanocrystals is ±5% for solutions. The efficiencies of non-transparent material, such as powder, together with the above-mentioned transparent materials were measured using the traditional integrating sphere method. Comparison of the two values showed that the traditional integrating sphere method usually underestimates the efficiency of powder samples ca. 10-20% depending on the optical density of the powder. This is because the emissions from more than ca. 0.2 mm deep do not leave the powder sample due to internal scattering. We also developed a method to overcome this problem