A positively chargeable single-layer electrophotographic photosensitive member includes a single-layer photosensitive layer. The single-layer photosensitive layer contains a charge generating material, a hole transport material, an electron transport material, and a binder resin. The electron transport material contains two or more compounds selected from the group consisting of compounds represented by the chemical formulas (1) to (4) below. ##STR00001##

An electrophotographic photosensitive member includes a support, an undercoat layer formed directly on the support, and a photosensitive layer formed on the undercoat layer, wherein when an ionization potential of the undercoat layer is represented by IPu, the IPu is 6.0 eV or higher, when an ionization potential of the support is represented by IPs, the IPs is lower than the IPu, the undercoat layer contains a compound (), when an ionization potential of the compound () is represented by IP, the IP is 5.0 eV or higher and 5.4 eV or lower, and the IPs and the IP satisfy the following relational expression (1):

[00001]$\begin{array}{cc}\mathrm{IPs}\mathrm{IP}-1..& \left(1\right)\end{array}$

An electrophotographic photoreceptor includes a conductive support; and an undercoat layer and a photosensitive layer stacked on the conductive support, in which the undercoat layer contains crystalline electron transport compound particles. In X-ray diffraction measurement performed on the undercoat layer in a thickness direction, a maximum intensity peak has a half-width of 5 or less, and a maximum value Nmax among orientation indices N expressed by equation (1) below is 1 or more and 3 or less: $\begin{array}{cc}\mathrm{Orientation}\mathrm{index}=\frac{\frac{I_1}{.Math.I_1}}{\frac{I_2}{.Math.I_2}}& \left(1\right)\end{array}$ where I.sub.1 represents a relative integral intensity of each of peaks in the X-ray diffraction measurement performed on the undercoat layer in the thickness direction, and I.sub.2 represents a relative integral intensity of each of peaks in X-ray diffraction measurement performed on the undercoat layer processed into a powder form having a volume-average particle diameter of 5m or less.

An electrophotographic photoreceptor includes a conductive substrate, a first undercoat layer that is provided on the conductive substrate, a second undercoat layer that is provided on the first undercoat layer, and a photosensitive layer that is provided on the second undercoat layer, in which the first undercoat layer contains at least one electron transport material selected from the group consisting of a compound represented by Formula (1), a compound represented Formula (2), and a compound represented by Formula (3), and a binder resin, and a content of silica particles in the first undercoat layer is 0% by mass or 5% by mass or less, and the second undercoat layer contains at least one electron transport material selected from the group consisting of the compound represented by Formula (1), the compound represented Formula (2), and the compound represented by Formula (3), silica particles, and a binder resin, and a content of the silica particles in the second undercoat layer is larger than the content of the silica particles in the first undercoat layer.

##STR00001##

In Formula (1), R.sup.11, R.sup.12, R.sup.13, R.sup.14, R.sup.15, R.sup.16, R.sup.17, and R.sup.18 each independently represent a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, an aryl group, an aryloxy group, an alkoxycarbonyl group, an aryloxycarbonyl group, an alkoxycarbonylalkyl group, an aryloxycarbonylalkyl group, or a halogen atom, R.sup.11 and R.sup.12, R.sup.12 and R.sup.13, or R.sup.13 and R.sup.14 may be each independently linked to each other to form a ring, and R.sup.15 and R.sup.16, R.sup.16 and R.sup.17, or R.sup.17 and R.sup.18 may be each independently linked to each other to form a ring.

In Formula (2), R.sup.21, R.sup.22, R.sup.23, R.sup.24, R.sup.25, R.sup.26, R.sup.27, and R.sup.28 each independently represent a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, an aryl group, an aryloxy group, an alkoxycarbonyl group, an aryloxycarbonyl group, an alkoxycarbonylalkyl group, an aryloxycarbonylalkyl group, or a halogen atom, R.sup.21 and R.sup.22, R.sup.22 and R.sup.23, or R.sup.23 and R.sup.24 may be each independently linked to each other to form a ring, and R.sup.25 and R.sup.26, R.sup.26 and R.sup.27, or R.sup.27 and R.sup.28 may be each independently linked to each other to form a ring.

In Formula (3), R.sup.31, R.sup.32, R.sup.33, R.sup.34, R.sup.35, R.sup.36, R.sup.37, and R.sup.38 each independently represent a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, an aryl group, an alkoxycarbonyl group, or a halogen atom.